De-fragmentation of transmission sequences

ABSTRACT

The present invention aims at avoiding fragmentation during transmission of a structured document ( 10 ). This is achieved by a method of progressive transmission for a structured document ( 10 ). the structured document ( 10 ) comprising sub-documents ( 12, 14, 16 , . . . ) with related relevance weightings. In particular, a fragmentation measure is determined according to the transmission sequence in an automatic manner using a formal expression of fragmentation. After comparison the fragmentation measure with a predetermined threshold value the transmission sequence is modified to reduce fragmentation when the fragmentation measure exceeds the threshold value.

FIELD OF INVENTION

The present invention relates to a method of progressive transmissionfor a structured document and related de-fragmentation strategiesapplied to transmission sequences.

BACKGROUND ART

In WO01/46813 A1, there is described a communication system fordownloading a structured document in which unit documents of thestructured documents of related to one another hierarchically and arestored in a server device. A terminal device acquires and displays oneof the structured documents. The server device and the terminal deviceare interconnected through a network to constitute a communicationsystem. Further, the terminal device notifies the server device of theidentifier of a document that the user gives an instruction to display.In view of this, the server device then sends the next document of thestructured document for subsequent storage in the terminal device.

Further, in U.S. Pat. No. 5,895,476, there is described a design enginefor automatic reformatting for design and media in support of automaticrendering multiple forms of media such as print.

In Girardot M. et al.: ‘Efficient representation and streaming of XMLcontent over the Internet medium’, Multimedia And Expo, 2000, ICME 2000,2000 IEEE International Conference On New York, N.Y., USA, 30 Jul.- 2Aug. 2000, Piscataway, N.J., USA, IEEE, U.S., 30 Jul. 2000, pages 67-70,XP010511404, ISBN: 0-7803-6536-4, there is described an efficientrepresentation and streaming of XML content over the Internet medium.

Therefore, the further improvement of efficient web-enabled multimediadatabases and middleware systems is a major topic in today's computerscience research. The transmission and management of multimedia contentdiffers essentially from handling numeric and character transmissiondata in communication systems and requires new strategies in handlingmultimedia data before transmission thereof.

This is particularly the case for so-called structured documents forwhich a transmission sequence is determined before transmission thereof.For structured documents it is assumed that related sub-documents havedifferent hierarchy levels and that on each hierarchy level a partitionand re-ordering of sub-documents may lead to severe fragmentations.

To explain this problem, further details of fragmentation will beexplained in the following with respect to FIG. 1 to 4.

As shown in FIG. 1, a typical example of a structured document 10comprises a plurality of sub-documents, e.g., a headline 12, a subtitle14, an image 16 with a related caption 18, web-links 20 and differenttext sections 22, 24, 26, 28.

To improve transmission of such structured documents it has proven to beefficient to model the structure imposed on the structured document,e.g., using a tree-structure as shown in FIG. 2.

As shown in FIG. 2, the document as a whole is related to the root node.Further, the different sub-documents referred to above with FIG. 1 aremodelled as nodes in the tree on lower levels of hierarchy. Here, onespecific hierarchy level in the tree modelling a structured documentwill also be referred to as a level of detail node in the following.

A further concept applied to structured documents is relevanceweighting. The main goal of relevance weighting is to provide an optimaltransmission order for sub-documents during transmission, e.g., due tothe possibly limited capacity in mobile communication environments likelow band width.

Another example for the application of relevance weightings are end userinterests where more relevant parts of structured documents should bedelivered first. Therefore, relevance weightings are applied to identifycontent-bearing sub-documents, so that subsequently the documentstructure may be altered in a way that highly weighted sub-documentswill be delivered first.

FIG. 3 shows the impact of relevance weightings on readability ofdocuments after transmission thereof. The left figure of FIG. 3 isrelated to the natural reading sequence intended for natural reading ofsub-documents, identified by the author of the structured document.Here, the abscissa identifies the number of sub-documents and theordinate the related relevance weighting of each single sub-document.The right side of FIG. 3 shows. the distribution of relevant weightingsafter reordering the sub-documents according to their relevanceweighting.

As shown in FIG. 4 the simplistic application of relevance weightings tosub-documents before progressive transmission thereof may lead to a highgrade of fragmentation of the structured documents as seen by the enduser.

In particular, this is a problem for progressive transmission to adevice having limited display capabilities, i.e., a mobile phone, apersonal digital agent PDA, a portable computer, or a hybrid thereof.The display typically has a scroll bar 28 for triggering the display ofthe transmitted structured document. When scrolling the scroll bar fromthe upper side to the lower side, different parts of the transmittedstructured document will be displayed to the user.

As shown in FIG. 4, relevance weightings may lead to a situation where,e.g., the image 18 shown in FIG. 1 is no longer displayed with therelated head line. This fragmentation of the structured document leadsto a significant decrease in perceivability after progressivetransmission.

SUMMARY OF INVENTION

In view of the above, an object of the invention is to avoidfragmentation during transmission of a structured document.

A further object of the present invention is, to provide strategies forde-fragmenting a structured document after re-ordering thereof accordingto relevance weightings.

According to a first aspect of the invention as defined in claim 1,these objects are achieved through a method of progressive transmissionfor a structured document. The structured document comprisessub-documents with related relevance weightings. Without restricting thescope of the invention, it may be assumed that a transmission sequencefor the sub-documents is generated according to relevance weightings.

According to the present invention it is proposed for the first time tomodify the transmission sequence derived according to relevanceweightings to improve perceivability for an end user after display ofthe structured document.

Heretofore, it is proposed to use a formal representation offragmentation which forms the basis of automation of thede-fragmentation process.

Once a formal measure of fragmentation is available it may then becompared with a threshold value. As soon as fragmentation exceeds thethreshold, a de-fragmentation strategy may then be applied to thepreliminary transmission sequence. It is important to note that thepresent invention is not restricted to a particular type ofde-fragmentation strategy.

According to a preferred embodiment, sub-documents of the structureddocument are modelled as nodes of an ordered tree, the number ofsub-documents being k, and progressive transmission is achieved on alevel of detail of the tree selected for document transmission.

According to the preferred embodiments outlined above it is possible toapply easily different levels of abstraction of the structured documentcontents before transmission thereof. The lower the level of detail inthe tree selected for document transmission, the more detailed theinformation provided to the end user will be. Therefore, in particularfor lower levels of detail for document transmission thede-fragmentation strategies explained in the following are of particularrelevance.

According to another preferred embodiment, a reading sequence accordingto an intended reading ordering of sub-documents is an ordered set ofnodes on the level of detail of the tree R=[r₁, . . . ,r_(k)], thetransmission sequence for progressive transmission is an ordered set ofnodes on a level of detail of the tree D=[d₁, . . . ,d_(k)], and thefragmentation measure is determined using a permutation vector π:{l, . .. ,k}→{l, . . . ,k} defined according to π(i)=j, with r_(i)=d_(i) for i,jε{l, . . . ,k}.

This preferred embodiment is related to a formalized approach to therepresentation of reading sequences and transmission sequences. Further,it relates to the application of a permutation vector onto suchsequences as a pre-requisite for applying the formal measure offragmentation to different de-fragmentation strategies.

According to another preferred embodiment, the fragmentation measure isan absolute fragmentation measure defining the sum of distances ofsub-components from their original position in the reading vector.

The advantage of this preferred embodiment is that the fragmentationmeasure may easily be determined simply through one scan of thepermutation vector as outlined above. Further, it gives an indication onnecessary de-fragmentation of sub-documents before transmission thereof.

According to another preferred embodiment, the fragmentation measure isa ratio of incoherence measuring how far absolute positions of nodes inthe reading sequence are changed after generation of the transmissionsequence.

The perception of the end user is improved if those sub-documents whichhave originally been arranged adjacent or again arranged adjacent aftertransmission of the structured document, i.e. with a low degree ofincoherence. Therefore, this ratio of incoherence as fragmentationmeasure has the advantage that it is directly related to the perceptionof the end user.

According to another preferred embodiment, the fragmentation measure isa readability measure expressing how many nodes in the transmissionsequence are still in the order according to the reading sequence.

This measure of fragmentation has the advantage that it gives anindication of the absolute number of sub-documents which maintain thereading sequence also after transmission.

Preferably, the different fragmentation measures may be normalized.

The normalization of the different fragmentation measures isadvantageous in that the fragmentation measure becomes independent ofthe document size.

According to another preferred embodiment of the present invention,sub-documents comprise data defined according to the document model fora specific application.

This preferred embodiment of the present invention allows to achievede-fragmentation of structured documents designed for any kind ofapplication. In other words, the different concepts of measuringde-fragmentation and related de-fragmentation strategies may be appliedto any type of application. Typical examples for sub-documents, which,however, are not to be construed at limiting the present invention, arehead line, author, title, image, photo, and/or text sub-documents.

According to another preferred embodiment of the present invention,progressive transmission is achieved to a mobile device, e.g., a mobiletelephone, a personal digital agent, a portable computer or any type ofhybrid device.

Therefore, the present invention may be adapted to any type oftransmission irrespective of the transmission target. The application ofthe present invention is of particular advantage when the transmissiontarget has limited display capabilities, which, without loss ofgenerality, may be assumed for typical examples for mobile devices suchas mobile telephone, personal digital agents PDAs, portable computers orany type of hybrid device.

According to another embodiment of the present invention, structureddocuments are submitted for progressive transmission with a markuplanguage selected from a group comprising WAP, HTML, cHTML, or XML.

This preferred embodiment of the present invention is related to typicalapplication scenarios of the present invention, however, withoutlimiting the scope thereof. E.g., HTML may be well suited for internetapplications. WAP is applicable to the transmission of structureddocuments in GSM to mobile devices. A further example is the applicationof cHTML which may form a basis for application of the method oftransmitting structured documents within imode applications, e.g.,within IMT 2000. Further, imode structured document transmission mayalso be based on. generic XML formats and generic XML documents.

According to another embodiment of the present invention, progressivetransmission is achieved via a connection provided according to astandard selected from a group comprising GSM, PDC, GPRS, PPP, HSCSD,WLAN, HiperLAN, IrDa, Bluetooth, IS 45, IS 95, IMT 2000.

This preferred embodiment of the present invention is particularlysuited for mobile communication applications and delivery of structureddocuments to mobile devices. Here, GSM, PDC, GPRS, IS 45, HSCSD, arestandards underlying the mobile communication. The same applies to IS 95and IMT 2000 for wideband CDMA.

However, the present invention is as well applicable to wireless localarea network applications such as WLAN, HiperLAN.

Further examples of the transmission of structured documents to end userdevices on the basis of mobile communication are infrared transmissionaccording to IrDa or short range mobile communication using theBluetooth standard.

Irrespective of the kind of device which receives document data and thedifferent embodiments outlined above, the present invention isparticularly suited for application of the client/server architecturewhere, e.g., the method of progressive transmission would be applied atthe server side, e.g., a content delivery server.

According to a further aspect as defined in claim 18, the presentinvention relates to a method of de-fragmenting a transmission sequenceto transmit a structured document. The structured document comprisessub-documents being modelled as nodes of a tree. Context linkagesbetween different sub-documents are modelled as edges of the tree, andthe transmission sequence is modelled as an ordered set of nodes on alevel of detail of the tree selected for document transmission, Themethod determines the total number of nodes in the tree and adjusts therelevance weighting for each node on the level of detail as a functionof a node number.

In the most general sense, the function of the node number is adecreasing function according to the order of the node being processed,e.g., the node number.

This first strategy for de-fragmentation allows to reduce documentfragmentation according to a preliminary transmission sequence havingregard to the overall structural characteristics of structureddocuments.

In particular, the first de-fragmentation strategy allows to considerthe natural intended reading sequence to achieve de-fragmentation.

Of particular advantage is the application of this firstde-fragmentation strategy to mobile environments.

Due to restricted band width and capabilities of mobile devices thelevel of detail for the delivery of sub-documents is often chosen low.However, the lower the level detail, the higher the risk of heavyfragmentation. This is one reason, why the de-fragmentation strategyoutlined above is of particular advantage.

According to another preferred embodiment, in the de-fragmentationmethod the tree is traversed in prefix order to assign a node number toeach node in the tree.

This preferred embodiment of the present invention is based on theassumption that sub-documents in the structured document have ahierarchy implied. Therefore high levels in the tree represent lessdetailed information than the lower levels in the tree. The relevance ofinformation is then reflected by the number of the related nodes in thetree.

It is therefore natural to use this information of relevance foramendment of relevance weightings of sub-documents. Once, relevanceweightings of the different nodes have been adjusted or equivalentlymodified the preliminary transmission sequence may be amendedcorresponding to the amended relevant weightings.

According to an another preferred embodiment of the de-fragmentationmethod the relevance weighting for each node is adjusted when traversingthe tree in prefix order to assign a node number to each node in thetree.

This preferred embodiment of the present invention has the advantagethat it requires only one traversal of the tree, both, for assigning thenode number and also for adjusting the relevance weighting of each node.This decreases complexity of the de-fragmentation procedure.

According to a preferred embodiment, relevance weightings for nodes areadjusted in indirect proportion to the number of the node, e.g., with afactor defined as the total number of nodes in the tree divided by thenumber of the node.

This preferred embodiment of the present invention is related to thefact that intuitively the relevance weighting of nodes on higher levelsof the tree should be raised more than the relevance weighting of nodeson lower levels of hierarchy of the tree being related to more detailedinformation.

According to a further aspect of the present invention as defined inclaim 24, there is proposed a second method of de-fragmenting atransmission sequence to transmit a structured document. The structureddocument comprises sub-documents with related relevance weightings beingmodelled as nodes of a graph. The context linkages between differentsub-documents are modelled as arcs of the graph, and the transmissionsequence being modelled as an ordered set of nodes. In a first step thenode with highest relevance weighting is selected as next node of ade-fragmented transmission sequence. Then in a second step a distancemeasure from the selected node to nodes of the transmission sequencewhich are not assigned to the de-fragmented transmission sequence isdetermined using the graph modelling of the structured document andshortest path metrics. In a third step relevance weightings for nodeswhich are not assigned to the de-fragmented transmission sequence areadjusted as a function of the related distance measure. The first tothird step are then recursively repeated until all nodes of thetransmission sequence are processed.

The first de-fragmentation method outlined above considers a readingsequence of a structured document. Supplement hereto, this secondde-fragmentation method is not restricted to a single level of hierarchyin a tree but allows to generalize the concept to a general graph or toseveral levels of hierarchy in a tree.

In particular, an adjustment of relevance weightings is carried outmultiple times to even more accurately use structural informationavailable to describe a document.

According to a preferred embodiment relevance weightings for nodes whichare not assigned to the de-fragmented transmission sequence are adjustedin indirect proportion to the related distance measure, e.g., bydividing the relevance weighting of the node through the distancemeasure to the selected node.

This preferred embodiment of the invention allows for appropriateselection of the next node during recursive processing of thetransmission sequence. According to the selection of the next node,distances from this node will then be determined to those elements of.the transmission sequence which have not been processed so far.

A first advantage is the flexible selection of the next node accordingto the highest relevance weighting, which may have been modifiedpreviously during de-fragmentation.

A second advantage is the re-calculation of relevance weightings toachieve the most appropriate picture of sub-document context at therelevant stages of the recursive de-fragmentation process.

Overall, this further de-fragmentation method according to the presentinvention allows for a dynamic adaptation of relevance weightings.

According to another preferred embodiment of the present invention thereis provided a computer program product directly loadable into theinternal memory of a content delivery device comprising software codeportions for performing the inventive progressive transmission andde-fragmenting steps when the product is run on a processor of thecontent delivery device. Preferably, the content delivery device may bea content delivery server or a content delivery portable computingdevice.

Therefore, the present invention is also provided to achieve animplementation of the inventive method steps on computer or processorsystems. In conclusion, such implementation leads to the provision ofcomputer program products for use with a computer system or morespecifically a processor operated in, e.g., a mobile communicationenvironment.

This programs defining the functions of the present invention can bedelivered to a computer/processor in many forms, including, but notlimited to information permanently stored on non-writable storage media,e.g., read only memory devices such as ROM or CD ROM discs readable byprocessors or computer I/O attachments; information stored on writablestorage media, i.e. floppy discs and harddrives; or information conveyto a computer/processor through communication media such as networkand/or and/or Internet and/or telephone networks via modems or otherinterface devices. It should be understood that such media, whencarrying processor readable instructions implementing the inventiveconcept represent alternate embodiments of the present invention.

DESCRIPTION OF DRAWING

Preferred embodiments of the present invention will be described in thefollowing with reference to the drawings in which

FIG. 1 shows an example for a structured document and the sub-documentsforming part thereof;

FIG. 2 shows a modelling of the structured document using a tree model;

FIG. 3 shows a distribution of relevance weightings in a structureddocument according to a natural reading sequence and a distributionafter re-ordering in compliance with relevance weighting;

FIG. 4 shows the impact of fragmentation after re-ordering thestructured document in compliance with the weighting on the display ofthe structured document;

FIG. 5 shows a schematic diagram of a transmission apparatus accordingto the present invention;

FIG. 6 shows a flowchart of a method for progressive transmissionaccording to the present invention;

FIG. 7 shows an example of a first de-fragmentation strategy accordingof the present invention;

FIG. 8 shows a flowchart for a first de-fragmentation method accordingto the present invention;

FIG. 9 shows an example for a second de-fragmentation strategy accordingto the present invention;

FIG. 10 shows an recursion of de-fragmentation according to the exampleshown in FIG. 9;

FIG. 11 shows a schematic diagram of a de-fragmentation apparatusaccording to the present invention;

FIG. 12 shows a flowchart for a second de-fragmentation method accordingto the present invention;

FIG. 13 shows an example of application of the present invention to aclient/server environment;

FIG. 14 shows results achieved through application of the presentinvention; and

FIG. 15 shows further results achieved through application of thepresent invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the following preferred embodiments of the invention will bedescribed with reference to the drawing.

Heretofore, different formal expressions for measuring documentfragmentation be will explained in the beginning.

Then the application of such formal expressions within a method forprogressive transmission will be described with reference to FIGS. 5 and6.

Hereafter different de-fragmentation methods according to the presentinvention will be described with reference to FIG. 7 to 13, followed bya discussion of results with respect to FIGS. 14 and 15.

As outlined above, one way to represent structured documents is a treemodel where the number of sub-documents in the structured document is k.Optionally, progressive transmission is achieved with respect to onelevel of hierarchy in the tree selected for document transmissionreferred to as level of detailed in the following.

Using this notation, a reading sequence according to an intended readingordering of sub-documents is an ordered set of nodes on the level ofdetail in the tree:R=[r_(l), . . . ,r_(k)],

Further, the transmission sequence for progressive transmission is anordered set of nodes on the level of detail of the tree according toD=[d_(l), . . . ,d_(k)],

A basis for determination of the fragmentation measure is the use of apermutation vectorπ:{l, . . . ,k}→{l, . . . ,k}defined according toπ(i)=j, with r_(i)=d_(j) for i,jε{l, . . . ,k}.

A first example for a fragmentation measure is an absolute fragmentationmeasure defining the sum of distances of sub-components from theiroriginal positions in the reading sequence according to$F_{abs} = {\sum\limits_{i = 1}^{k}{{{{\pi(i)} - i}}.}}$

An estimate for an upper bound of this absolute fragmentation measure is$F_{abs} \leq {\frac{\left( {k - 1} \right)^{2}}{2}.}$

This upper bound may be achieved to define a normalized absolutefragmentation method, being independent from document length, accordingto $F_{rel} = {\frac{2}{\left( {k - 1} \right)^{2}}{F_{abs}.}}$

Another example for a fragmentation measure is a ratio of incoherencemeasuring how far absolute positions of nodes in the reading sequenceare changed after generation of the transmission sequence. The ratio ofincoherence is defined according to$Z_{abs} = {\sum\limits_{i = 1}^{k - 1}{{{\pi\left( {i + 1} \right)} - {\pi(i)}}}}$

An upper bound of this ratio of incoherence may be estimated to$Z_{abs} \leq \frac{k \cdot \left( {k - 1} \right)}{2}$

Again, this upper bound may be used to determine a normalized ratio ofincoherence being independent of document length according to$Z_{rel} = {\frac{2}{k \cdot \left( {k - 1} \right)} \cdot {\left( {Z_{abs} - \left( {k - 1} \right)} \right).}}$

Yet another example for a fragmentation measure is a readability measureexpressing how many nodes in the transmission sequence are still in theorder according to the initial reading sequence after applying theinitial relevance weightings according to$S_{abs} = {\sum\limits_{i = 1}^{k - 1}{\begin{Bmatrix}{1,} & {{{{if}\quad{\pi\left( {i + 1} \right)}} - {\pi(i)}} = 1} \\{0,} & {otherwise}\end{Bmatrix}.}}$

Again, this fragmentation measure may be normalized to avoid dependencyon document length according to$S_{rel} = {\frac{1}{k - 1} \cdot S_{abs}}$

In the following, it will be explained how such formal expressions ofdocument fragmentation may be applied in a transmission apparatus forprogressive transmission according to the present invention.

As shown in FIG. 5, the transmission apparatus 30 comprises a memoryunit 32 adapted to store the structured document with sub-documents andrelated relevance weightings and further a transmission sequence for thesub-documents.

As shown in FIG. 5, the transmission apparatus 30 further comprises afragmentation measurement unit 34 adapted to use one of the formalexpressions of fragmentation outlined above for a measurement offragmentation in a transmission sequence, once relevant relevanceweightings have been applied to re-order sub-documents and thepreliminary transmission sequence has been adapted accordingly.

As shown in FIG. 5, the transmission apparatus 30 further comprises ade-fragmentation unit 36 adapted to compare the determined fragmentationmeasure with a threshold value and further adapted to apply ade-fragmentation strategy when the fragmentation measure exceeds thethreshold value.

As shown in FIG. 5, the transmission apparatus 30 further comprises aninterface unit 38 adapted to exchange of transmission data, i.e. eitherto receive a preliminary transmission sequence and related structureddocument information or to forward the structured document to the enduser when the transmission sequence is determined.

The operation of the transmission apparatus shown in FIG. 5 will beexplained with reference to the flow chart shown in FIG. 6. FIG. 6 showsa flowchart according to operation of the transmission apparatus shownin FIG. 5.

As shown in FIG. 6 in a step S10 there is generated a transmissionsequence as starting point for the method of progressive transmissionaccording to the present invention. Alternatively, this transmissionsequence may be provided as input to the method of progressivetransmission.

Then, in a step S12, the different formal expressions of fragmentationsare used to determine a fragmentation measure. It should be noted, thatsuch a formalization is the basis for the determination of thefragmentation measure in an automatic manner. It is also the basis forthe application of de-fragmentation methods according to the presentinvention to be discussed in more detail in the following with referenceto FIG. 7 to 12.

As shown in FIG. 6, in a step S14 the determined fragmentation measureis compared to a threshold value. If the threshold value exceeded, ade-fragmentation strategy is applied in step S16 before progressivetransmission in step S18. Otherwise, the method will directly proceedfrom the interrogation step S14 to step 18 for progressive transmission.

In the following, further details of de-fragmentation according to thepresent invention will be explained with respect to FIG. 7 to 12. Inparticular, FIGS. 7 and 8 relate to a first de-fragmentation methodaccording to the present invention, and FIG. 9 to 12 relate to a secondde-fragmentation method according to the present invention.

FIG. 7 shows an example for the application of the firstde-fragmentation method according to the present invention.

For the example shown in FIG. 7 it is assumed that the structureddocument comprises sub-components being modelled as nodes 1, . . . , 8of a tree. Context linkages between different sub-documents are modelledas edges of the tree, and the transmission sequence is modelled as anordered set of nodes on a level of detail, e.g., node 2 and 6 or node 3,4, 5, 7, 8, of the tree which is selected for document transmission.

As shown in FIG. 7, initially there is determined the total number ofnodes in the tree, which for the example is 8.

Further, each node in the tree has assigned a node number 1, . . . , 8according in a prefix order. A first option is that the document relateddata contains this information. A second option is that the node numbersare assigned during a prefix order traversal of the tree.

Once the total number of nodes in the tree and a node numbering isavailable, it is possible to adjust the relevance weighting for eachnode, and therefore also for each sub-document, on the level of detailselected for document transmission as a function of the node number.

Once such example for a function is that relevance weightings areadjusted in indirect proportion to the number of the node, e.g., foreach node according to total number of nodes in the tree divided by therelated node number.

Assuming that the level of detail for the example shown in FIG. 7 is 2,the initial relevance weightings would be updated from 18, 16, 20, 49,50, respectively, to 48, 32, 32, 56, 50, respectively.

According to a generalization of the example shown in FIG. 7, one couldconsider a real number a divided by the node number.

From the example given above it may be understood that the adjustment ofrelevance weightings requires a traversal of the tree. According to thepresent invention where node numbers are provided for nodes throughtraversing the tree, already during this traversal of the treesimultaneously relevance weightings may be adjusted in the senseoutlined above to reduce complexity.

FIG. 8 shows a flowchart representation of the fragmentation methodillustrated with respect to FIG. 7.

As shown in FIG. 8, in the first step S20 the total number of nodes inthe tree is determined. In a second step S22, a node number is assignedto each node in the tree, where step S22 is optional when the relateddata is already available from the information regarding the structureddocument. Then, in step S24 the relevance weightings of nodes in thetrees are adjusted for de-fragmentation.

In the following, a procedural representation for traversing the tree inprefix orders and a related modification of relevance weightings ofnodes in the tree will be given using a pseudo code representation.

A first procedure is the procedure prefix having the followingrepresentation: 1.  procedure prefix (n:Node, p:N):N 2.  Begin 3.  pos(n) := p; last := p; 4.   chldrn := children (n); 5.   while(chldrn <> [ ] ) do 6.    last := prefix (head(chldrn), last + 1); 7.   chldrn : = tail (chldrn); 8.   end 9.   return last; 10.  EndThe procedure prefix receives a list of nodes and the initial number forthe root node, e.g., a value of one. According to line 1 and 6, theprocedure prefix is recursively applied to traverse the tree in prefixorder.

To achieve this, at every initialization of the procedure prefix, toeach node there will assigned a node number, referred to as pos in line3, and its value is memorized in a variable last.

Also, there is set up a list of children as list of children of thecurrent node, line 4. While this list is a non-empty list, the procedureprefix will be recursively applied to the elements of the list, line 6,this time using the list of children and an incremented number node(last+1) as calling parameters.

To traverse the different levels of hierarchy of the tree down to theleaf nodes, the list of children is modified to the tail of this list,line 7. For each call of the procedure prefix the last number assignedto a node during a traversal of the sub-tree is returned, line 9.

In the following, there will be explained a modified procedure S-ORDERwhich also allows to modify relevance weightings of nodes at the sametime when assigning node numbers to the nodes of the tree. The pseudocode representation thereof is 1.  procedure S-ORDER (n:Node, p:N):N 2. Begin 3.    pos(n) := p; last := p; 4.    v(n) := (total/pos(n))*v(n);5.    chldrn := children (n); 6.    while (chldrn <> [ ] ) do 7.    last:= S-ORDER (head(chldrn), last + 1); 8.    chldrn : = tail (chldrn); 9.  end 10.   return last; 11.  End

Here, an additional command is added, line 4, to modify the weight of anode. The modification is achieved by multiplying an initial relevanceweighting with the total number of nodes in the tree and then dividingit by the node number assigned to the node. It is should that this is annon-limiting example only and that any type of relevance weightingupdate is applicable in the procedure S-ORDER.

The further steps of the modified procedure prefix are the same asoutlined above.

The advantage of the procedure S-ORDER is that only one traversal of thetree is necessary when node numbers are not input to the method ofde-fragmentation outlined above, thus reducing complexity.

In the following, a further embodiment for the de-fragmentation methodaccording to the present invention will be explained with reference toFIGS. 9 to 12.

Heretofore, FIG. 9 shows an example to illustrate the application ofthis further de-fragmentation method to a tree modeling the structure ofa structured document, where the level of detail is 2, the nodesrepresenting documents for progressive delivery are 3, 4, 5, 7 and 8.

Further, it is assumed that the initial relevance weightings of thesenodes are 192, 176, 160, 195 and 100, respectively.

According to the further de-fragmentation strategy it is proposed toselect the node with highest relevance weightings, i.e. node 7 withrelevance weighting 195, as next node during generation of ade-fragmented transmission sequence.

Then, a distance from this selected node, e.g., node 7, in the sense ofa shortest path metric is determined to different nodes in the tree,i.e. a distance 1 to node 6, a distance 2 to node 8, etc.

Then, relevance weightings of the remaining nodes are updated accordingto the related distance.

The result of this step is shown in tabular form in FIG. 10.

FIG. 10 shows that during each iteration one node is assigned from thetransmission sequence D to a de-fragmented transmission sequence D′. Thesame table also shows that the nodes in the transmission sequence notyet assigned to the de-fragmented transmission sequence D′ are sortedaccording to the values of the relevance weightings after updatethereof.

As shown in FIGS. 9 and 10, after assignment of the node 7 to thede-fragmented transmission sequence in a first step, the next node to beselected is node 3, having the highest relevance weighting 48 afterdivision of initial value 192 by the related distance value 4.Therefore, this node 3 will be assigned to the second place of thede-fragmented transmission sequence.

The further lines of the table in FIG. 10 show the recursive applicationof the de-fragmentation procedure explained above and the finalde-fragmented transmission sequence D′: 7, 8, 3, 4, 5.

FIG. 11 shows a schematic diagram of a de-fragmentation apparatus beingadapted to carry out the second de-fragmentation method according to thepresent invention, explained with an example referring to FIGS. 9 and10.

As shown in FIG. 11, the de-fragmentation apparatus comprises a memoryunit 42 and a processing unit 44. The processing unit 44 divides into aselection unit 45, a distance measurement unit 46, and an adjustmentunit 47.

FIG. 12 shows a flowchart for the second de-fragmentation method incompliance with the operation of the de-fragmentation apparatus shown inFIG. 11 and as explained with respect to FIGS. 9 and 10.

As shown in FIG. 12, according to the second de-fragmentation method ina first step S30 there is selected a node with highest relevanceweighting. Then, in a second step S32 distance measures are determinedfrom the selected node using the graph modeling of the structureddocument and shortest path metrics. Then, in a step S34 relevanceweightings are adjusted for nodes which are not yet assigned to thede-fragmented transmission sequence. The adjustment is achieved using afunction of the related distance measure.

As shown in FIG. 12, steps S30 to S34 are recursively applied until allelements of the progressive transmission sequence are transferred to thede-fragmented transmission sequence.

It should be noted, that according to the present invention there is noparticular restriction for the adjustment of relevance weightings in thenode.

In the most general sense, it is a decreasing function according to theorder of the node being processed, e.g., the node number. Therefore, oneimplementation would be to divide the relevance weight of a node by thedistance to the selected node, as outlined above.

A formal representation of the second de-fragmentation method accordingto the present invention is given in the following. Here, the procedureS-DISTANCE is recursively applied to a list of nodes of the tree asfollows: 1.  Procedure S-DISTANCE (D: List(Node)) 2.  Begin 3.  first:=head(D); rest:=tail(D); 4.   Foreach (c in rest) do 5.    v(c):= v(c)/dist(c,first); 6.   S-DISTANCE (sort(<=, v, rest)); 7.  End

In line 5 of the procedure S-DISTANCE the relevance weightings of thenodes not yet assigned to the de-fragmented transmission sequence areupdated, as explained above with reference to FIG. 9 to 12 and relatedembodiments of the present invention. It is should that this is annon-limiting example only and that any type of relevance weightingupdate is applicable in the procedure S-DISTANCE.

The recursive call of the S-DISTANCE procedure in line 6 uses a sortingprocedure providing the list of nodes for sub-sequent processing with anascending order of updated relevance weightings. Therefore, the nextnode to be selected for assignment to the de-fragmented transmissionsequence is the head of the list.

FIG. 13 shows an example of application of the present invention to aclient/server environment, in particular being related to mobilecommunication.

As shown in FIG. 13, progressive transmission as explained above isachieved to a mobile device, e.g., a mobile telephone, a personaldigital agent, a portable computer or any type of hybrid device.Although not shown, the present invention may also be applied to aclient/server environment in a fixed network.

As shown in FIG. 13, the mobile device may be of any type. Withoutlimiting scope of invention examples are mobile telephones, personaldigital assistants PDAs, portable computers or any type of hybrid (notshown).

According to another embodiment of the present invention, progressivetransmission is achieved via a connection provided according to astandard selected from a group comprising GSM, PDC, GPRS, PPP, HSCSD,WLAN, HiperLAN, IrDa, Bluetooth, IS 45, IS 95, IMT 2000.

This preferred embodiment of the present invention is particularlysuited for mobile communication applications and delivery of structureddocuments to mobile devices. Here, GSM, PDC, GPRS, PPP, IS 45, HSCSD,are standards underlying the mobile communication. The same applies toIS 95 and IMT 2000 for wideband CDMA.

However, the present invention is as well applicable to wireless localarea network applications such as WLAN, HiperLAN.

As shown in FIG. 13, communication between the server and the client iswireless without any restriction on the physical layer, e.g., accordingto mobile communication standards GSM, PDC, GPRS, PPP, HSCSD, IS 45, IS95, IMT 2000. Another example would be the application of local networkrelated standards WLAN, HiperLAN, Bluetooth, or infrared transmissionusing IrDA.

FIGS. 14 and 15 shows results achieved although application of thepresent invention.

In particular, FIG. 14 shows a measurement values for documentation forfour cases:

-   Case 1: document fragmentation after application of relevance    weightings to initial transmission sequence without application of    de-fragmentation methods according to the present invention;-   Case 2: document fragmentation after application of relevance    weightings to initial transmission sequence and application of the    first de-fragmentation method according to the present invention;-   Case 3: document fragmentation after application of relevance    weightings to initial transmission sequence and application of the    second de-fragmentation method according to the present invention;-   Case 4: document fragmentation after application of relevance    weightings to initial transmission sequence and application of the    first and second de-fragmentation method according to the present    invention;

FIG. 14 shows the results achieved for fifty different structureddocuments. The distribution of measurement values in the different casesand related normalized fragmentation values, i.e. absolute fragmentationmeasurement values, incoherence fragmentation measurement values, andreadability measurement value is respectively shown as line between alower limit value and an upper limit value. Mean values and variancesare illustrated using rectangles, where the middle line corresponds tothe mean value, respectively.

As shown in the upper part of FIG. 14, both the application of the firstde-fragmentation method and the second de-fragmentation method alreadyallow for a significant improvement of the absolute fragmentationmeasure and the incoherence fragmentation measure. At the same time, thereadability measurement value is improved considerably.

As shown in FIG. 15, the optimization of the different measurementvalues for document de-fragmentation has only little impact ondistributions of relevance weightings after applying thede-fragmentation methods according to the present invention. In otherwords, sub-documents with high relevance weights are still transmittedfirst within the progressive transmission method according to thepresent invention.

1-55. (canceled)
 56. A method of progressive transmission for astructured document, the structured document comprising sub-documentswith related relevance weightings, characterized by the steps:generating a transmission sequence for the sub-documents according torelevance weightings; determining a fragmentation measure according tothe transmission sequence in an automatic manner using a formalexpression of fragmentation; comparing the fragmentation measure with apredetermined threshold value; de-fragmenting the generated transmissionsequence when the fragmentation measure exceeds the threshold valueprior to transmission of the structured document.
 57. A method accordingto claim 56, characterized in that sub-documents of the structureddocument are modeled as nodes of a tree, the number of sub-documentsbeing k, and that progressive transmission is achieved on a level ofdetail of the tree selected for document transmission.
 58. A methodaccording to claim 57, characterized in that a reading sequenceaccording to an intended reading ordering of sub-documents is an orderedset of nodes on the level of detail of the treeR=[r_(l), . . . ,r_(k)], the transmission sequence for progressivetransmission is an ordered set of nodes on the level of detail of thetree D=[d_(l), . . . ,d_(k)], wherein the fragmentation measure isdetermined using a permutation vector π:{l, . . . ,k}→{l, . . . ,k}defined according toπ(i)=j, with r_(i)=d_(j) for i,jε{l, . . . ,k}.
 59. A method accordingto claim 58, characterized in that the fragmentation measure is anabsolute fragmentation measure defining the sum of distances ofsub-components from their original position in the reading sequenceaccording to $F_{abs} = {\sum\limits_{i = 1}^{k}{{{{\pi(i)} - i}}.}}$60. A method according to claim 59, characterized in that the absolutefragmentation measure is normalized into a relative fragmentationmeasure according to$F_{rel} = {\frac{2}{\left( {k - 1} \right)^{2}}{F_{abs}.}}$
 61. Amethod according to claim 58, characterized in that the fragmentationmeasure is a ratio of incoherence measuring how far absolute positionsof nodes in the reading sequence are changed after generation of thetransmission sequence, the ratio of incoherence being defined accordingto$Z_{abs} = {\sum\limits_{i = 1}^{k - 1}{{{{\pi\left( {i + 1} \right)} - {\pi(i)}}}.}}$62. A method according to claim 61, characterized in that the ratio ofincoherence is normalized into a relative ratio of incoherence accordingto$Z_{rel} = {\frac{2}{k \cdot \left( {k - 1} \right)} \cdot {\left( {Z_{abs} - \left( {k - 1} \right)} \right).}}$63. A method according to claim 58, characterized in that thefragmentation measure is a readability measure expressing how many nodesin the transmission sequence are still in the order according to thereading sequence, the readability measure being defined according to$S_{abs} = {\sum\limits_{i = 1}^{k - 1}{\begin{Bmatrix}{1,} & {{{{if}\quad{\pi\left( {i + 1} \right)}} - {\pi(i)}} = 1} \\{0,} & {otherwise}\end{Bmatrix}.}}$
 64. A method according to claim 63, characterized inthat the readability measure is normalized into a relative readabilitymeasure according to $S_{rel} = {\frac{1}{k - 1} \cdot {S_{abs}.}}$ 65.A method according to one of the claims 56 to 64, characterized in thatthe fragmentation measure is determined for nodes on a level of detailof the tree selected for document transmission.
 66. A method accordingto claim 65, characterized in that the level of detail is specifiedthrough a distance from a root node of the tree.
 67. A method accordingto claim 56, characterized in that sub-documents comprise data definedaccording to the document model of an application.
 68. A methodaccording to claim 56, characterized in that progressive transmission isachieved to a mobile device having limited capabilities.
 69. A methodaccording to one of the claim 68, characterized in that the mobileclient is a mobile client, such as a mobile telephone, a personaldigital agent, a portable computer or a hybrid.
 70. A method accordingto claim 67, characterized in that the mobile client is described usingat least one attribute.
 71. A method according to one of the claim 56,characterized in that structured documents are submitted for progressivetransmission with a markup language selected from a group comprisingWAP, HTML, cHTML, or XML.
 72. A method according to claim 56,characterized in that progressive transmission is achieved via aconnection provided according to a standard selected from a groupcomprising GSM, PDC, GPRS, PPP, HSCSD, WLAN, HiperLAN, IrDa, Bluetooth,IS 45, IS 95, IMT
 2000. 73. A method of de-fragmenting a transmissionsequence to transmit a structured document prior to transmission of thestructured document, the structured document comprising sub-documentsbeing modelled as nodes of a tree, the context linkages betweendifferent sub-documents being modelled as edges of the tree, and thetransmission sequence being modelled as an ordered set of nodes on alevel of detail of the tree selected for document transmission,comprising the steps: a) determining the total number of nodes in thetree; b) adjusting the relevance weighting for each node on the level ofdetail as a function of a node number.
 74. A method according to claim73, characterized in that it further comprises the step of traversingthe tree in prefix order to assign a node number to each node in thetree.
 75. A method according to claim 74, characterized in thatadjusting the relevance weighting for each node is achieved whentraversing the tree in prefix order to assign a node number to each nodein the tree.
 76. A method according to one of the claims 73 to 75,characterized in that relevance weightings for nodes are adjusted inindirect proportion to the number of the node.
 77. A method according to76, characterized in that the relevance weighting for each node isadjusted with a factor defined to total number of nodes in the treedivided by number of the node.
 78. A method according to claim 73,characterized in that the level of detail is specified as distance froma root node of the tree.
 79. A method of de-fragmenting a transmissionsequence to transmit a structured document prior to transmission of thestructured document, the structured document comprising sub-documentswith related relevance weightings being modelled as nodes of a graph,the context linkages between different sub-documents being modelled asarcs of the graph, and the transmission sequence being modelled as anordered set of nodes, comprising the steps: selecting the node withhighest relevance weighting as next node of a de-fragmented transmissionsequence; determining a distance measure from the selected node to nodesof the transmission sequence which are not assigned to the de-fragmentedtransmission sequence using the graph modelling of the structureddocument and shortest path metrics; adjusting relevance weightings fornodes which are not assigned to the de-fragmented transmission sequenceas a function of the related distance measure; recursively repeating theprevious steps until all nodes of the transmission sequence areprocessed.
 80. A method according to claim 79, characterized in thatrelevance weightings for nodes which are not assigned to thede-fragmented transmission sequence are adjusted in indirect proportionto the related distance measure.
 81. A method according to claim 80,characterized in that the relevance weighting for each is adjusted bydividing the relevance weighting of the node through the distancemeasure to the selected node.
 82. A method according to one of theclaims 79 to 81, characterized in that the graph is a tree. 83.Transmission apparatus for progressive transmission of a structureddocument, comprising: a memory unit adapted to store the structureddocument comprising sub-documents with related relevance weightings anda transmission sequence for the sub-documents according to relevanceweightings; characterized by a fragmentation measurement unit adapted todetermine a fragmentation measure of the transmission sequence in anautomatic manner using a formal expression of fragmentation and tocompare the fragmentation measure with a predetermined threshold value;de-fragmentation unit adapted to re-arrange the transmission sequencewhen the fragmentation measure exceeds the threshold value prior totransmission of the structured document; an interface unit adapted toexchange transmission data according to the transmission sequence. 84.Transmission apparatus according to claim 82, characterized in that thememory unit is adapted to store sub-documents of the structured documentas nodes of a tree, the number of sub-documents being k, and a level ofdetail of the tree selected for progressive transmission. 85.Transmission apparatus according to claim 84, characterized in that thememory unit is adapted to store a reading sequence according to anintended reading ordering of sub-documents as an ordered set of nodes onthe level of detail of the tree R=[r_(l), . . . ,r_(k)], the memory unitis adapted to store the transmission sequence for progressivetransmission as an ordered set of nodes on the level of detail of thetree D=[d_(l), . . . ,d_(k)], and the fragmentation measurement unit isadapted to determine a fragmentation measure of the transmissionsequence using a permutation vector π:{l , . . . ,k}→{l, . . . ,k}defined according to(i)=j, with r_(i) =d_(j) for i,jε{l, . . . ,k}
 86. Transmissionapparatus according to claim 85, characterized in that the fragmentationmeasurement unit is adapted to determine as an absolute fragmentationmeasure defining the sum of distances of sub-components from theiroriginal position in the reading vector according to$F_{abs} = {\sum\limits_{i = 1}^{k}{{{{\pi(i)} - i}}.}}$ 87.Transmission apparatus according to claim 85, characterized in that thefragmentation measurement unit is adapted to normalize the absolutefragmentation measure into a relative fragmentation measure according to$F_{rel} = {\frac{2}{\left( {k - 1} \right)^{2}}{F_{abs}.}}$ 88.Transmission apparatus according to claim 84, characterized in that thefragmentation measurement unit is adapted to determine the fragmentationmeasure as a ratio of incoherence measuring how far absolute positionsof nodes in the reading sequence are changed after generation of thetransmission sequence, the ratio of incoherence being defined accordingto$Z_{abs} = {\sum\limits_{i = 1}^{k - 1}{{{{\pi\left( {i + 1} \right)} - {\pi(i)}}}.}}$89. Transmission apparatus according to claim 87, characterized in thatthe fragmentation measurement unit is adapted to normalize the ratio ofincoherence into a relative ratio of incoherence according to$Z_{rel} = {\frac{2}{k \cdot \left( {k - 1} \right)} \cdot {\left( {Z_{abs} - \left( {k - 1} \right)} \right).}}$90. Transmission apparatus according to claim 84, characterized in thatthe fragmentation measurement unit is adapted to determine thefragmentation measure as a readability measure expressing how many nodein the transmission sequence are still in the order according to thereading sequence, the readability measure being defined according to$S_{abs} = {\sum\limits_{i = 1}^{k - 1}{\begin{Bmatrix}{1,} & {{{{if}\quad{\pi\left( {i + 1} \right)}} - {\pi(i)}} = 1} \\{0,} & {otherwise}\end{Bmatrix}.}}$
 91. Transmission apparatus according to claim 89,characterized in that the fragmentation measurement unit is adapted tonormalize the readability measure into a relative readability measureaccording to $S_{rel} = {\frac{1}{k - 1} \cdot {S_{abs}.}}$ 92.Transmission apparatus according to claim 84, characterized in that thefragmentation measurement unit is adapted to determine the fragmentationmeasure for nodes on a level of detail of the tree selected for documenttransmission.
 93. Transmission apparatus according to one of the claims83 to 91, characterized in that the memory unit is adapted to storesub-documents data defined according to the document model of anapplication.
 94. Transmission apparatus according to one of the claims83 to 92, characterized in that the interface unit is adapted totransmit data to a mobile device.
 95. Transmission apparatus accordingto one of the claims 83 to 92, characterized in that the transmissionapparatus is a server and is adapted to transmit data to a clientdevice.
 96. Transmission apparatus according to claim 95, characterizedin that the client device is a mobile client.
 97. Transmission apparatusaccording to claim 96, characterized in that the memory unit is adaptedto store attribute information for the mobile device.
 98. Transmissionapparatus according to claim 83, characterized in that the interfaceunit is adapted to receive data being related to structured documentsfor subsequent progressive transmission using a markup language selectedfrom a group comprising WAP, HTML, cHTML or XML.
 99. Transmissionapparatus according to claim 83, characterized in that the interfaceunit is adapted to progressive transmission with a connection providedaccording to a standard selected from a group comprising GSM, PDC, GPRS,PPP, HSCSD, WLAN, HiperLAN, IrDa, Bluetooth, IS 45, IS 95, IMT 2000.100. De-fragmentation apparatus for de-fragmentation of a transmissionsequence for a structured document prior to transmission thereof,comprising: a memory unit adapted to store a structured document and amodel thereof, where sub-documents of the document are stored inrelation to nodes of a tree, context linkages between differentsub-documents are stored as edges of the tree, and the transmissionsequence is stored as an ordered set of nodes on a level of detail ofthe tree selected for document transmission; a processing unit adaptedto determine the total number of nodes in the tree; a de-fragmentationunit adapted to adjust the relevance weighting for each node on thelevel of detail as a function of a node number.
 101. De-fragmentationapparatus according to claim 100, characterized in that the processingunit is adapted to traverse the tree in prefix order and to store a nodenumber for each node in the tree in the memory unit. 102.De-fragmentation apparatus method according to claim 101, characterizedin that processing unit is adapted to adjust the relevance weighting foreach node in the memory unit when traversing the tree in prefix order.103. De-fragmentation apparatus method according to one of the claims100 to 102, characterized in that the processing unit is adapted toadjust relevance weightings for nodes in the memory unit in indirectproportion to the number of the node.
 104. De-fragmentation apparatusmethod according to 102, characterized in that the processing unit isadapted to adjust the relevance weighting for each node in the memoryunit with a factor defined to total number of nodes in the tree dividedby number of the node.
 105. A de-fragmentation apparatus forde-fragmentation of a transmission sequence of a structured documentprior to transmission thereof, comprising: a memory unit adapted tostore a model of the structured document, where sub-documents of thedocument and related relevance weightings are stored as nodes of agraph, context linkages between different sub-documents are stored asarcs of the graph, and the transmission sequence is stored as an orderedset of nodes; a processing unit having a selection unit adapted toselect a node with highest relevance weighting as next node of ade-fragmented transmission sequence; a distance measurement unit adaptedto determine a distance measure from the selected node to nodes of thetransmission sequence which are not assigned to the de-fragmentedtransmission sequence using the graph modelling of the structureddocument and shortest path metrics; an de-fragmentation unit adapted toadjusting relevance weightings for nodes which are not assigned to thede-fragmented transmission sequence as a function of the relateddistance measure; wherein the processing unit is adapted recursivelyactivate the selection unit, the distance measurement unit, and thede-fragmentation unit until all nodes of the transmission sequence areprocessed.
 106. A de-fragmentation apparatus according to claim 105,characterized in that the de-fragmentation unit is adapted to adjustrelevance weightings for nodes which are not assigned to thede-fragmented transmission sequence in indirect proportion to therelated distance measure.
 107. A de-fragmentation apparatus according toclaim 105, characterized in that the de-fragmentation unit is adapted toadjust relevance weightings for nodes which are not assigned to thede-fragmented transmission sequence by dividing the relevance weightingof the node with the distance measure to the selected node.
 108. Acomputer program product directly loadable into the internal memory of acontent transmission device, comprising software code portions forperforming the steps for progressive transmission according to claim 56,when the product is run on a processor of the content transmissiondevice.
 109. A computer program product directly loadable into theinternal memory of a content transmission device, characterized bycomprising software code portions for performing the steps forde-fragmenting a transmission sequence according to claim 73, when theproduct is run on a processor of the content transmission device.
 110. Acomputer program product according to claim 108, characterized in thatthe device is a server or a mobile device.